Obesity linked to increased inhalation of air pollutants

Researchers have long known that exposure to air pollution can cause respiratory illnesses, such as asthma. But a new study suggests that individuals who are overweight or obese breathe in up to 50% more air each day, compared with those of a healthy weight, meaning they are more vulnerable to air contaminants.

To reach their findings, published in the journal Risk Analysis, investigators from the School of Public Health at the Université de Montréal in Canada, led by Dr. Pierre Brochu, analyzed information from 1,096 participants aged between 5 and 96 years who were obese or overweight.

This information was compared with data collected from 902 participants of a normal, healthy weight.

Adults were classified according to the following body mass index (BMI) groups:

Normal weight (18.5-<25 kg/m2)

Overweight (25-<30 kg/m2)

Obese class 1 (30-<35 kg/m2)

Obese class 2 (35-<40 kg/m2)

Obese class 3 (40 kg/m2 or more).

The researchers assessed participants' urine samples to measure inhalation rates. This was done by measuring disappearance rates of two ingested tracers - deuterium and heavy oxygen.

The tracers were then used to measure the amount of carbon dioxide that each participant exhaled in real-life situations in their normal environment. This was measured every minute of the day from 7 to 21 days.

Results worrying, 'particularly for children'

The researchers found that overall, overweight and obese adults breathe in 7-50% more air every day, compared with adults of normal weight, while overweight and obese children breathe in 10-24% more air each day than children of normal weight.

Researchers say people who are overweight or obese breathe in up to 50% more air each day than those of a healthy weight - exposing them to more air pollutants.

Individuals who were obese class 2 were found to have the highest average air inhalation at 24.6 m3, compared with 16.4 m3 for adults of normal weight. According to the researchers, this means obese class 2 individuals are breathing in 50% more air pollutants.

Exposure to air contaminants, such as ammonia, sulphur dioxide, ozone and nitrogen dioxide, are known to be respiratory irritants that can cause illnesses such as asthma and other pulmonary diseases.

Dr. Brochu says that although the findings are of concern for obese adults, they are even more worrying for obese children.

He explains that children have a much higher metabolism relative to body weight than adults. This means they breathe in more air per kilogram of weight compared with adults. He says this also applies to men over women.

Obese individuals 'exposed to more air pollution than top athletes'

Previous research from Dr. Brochu revealed that a person who climbs Mount Everest needs an average of 19.8 m3 more air each day, while a cyclist taking part in the Tour de France breathes in around 45.9 m3 each day during the race period.

Findings from this study raised the question - could athletes be more vulnerable to air pollutants?

However, Dr. Brochu says athletes experience "peak inhalation" that is unable to be maintained every day of the year.

He explains:

"We observed that half of the type 2 obese cohort breathed 24.6-55 m3 of air every day, year after year, so it is clear that the amount of air they inhale every day exposes them to more contaminants than some top athletes."

Dr. Brochu says, however, it is unknown as to whether high inhalation rates may contribute to the development of respiratory illness for adults and children who are overweight or obese. But he plans to carry out further studies to see if this is the case.

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